The polytetrafluoroethylene (PTFE) fibers have a low friction coefficient and are excellent in heat resistance, chemical resistance, electric insulation, hydrophobic property and air permeability. The PTFE fibers have been used, for example, as a bag filter by forming into a woven fabric or a felt-like non-woven fabric. However, in case of the felt-like non-woven fabric, there was a problem that falling of fibers occurs easily because there is no bonding between them. Once the PTFE fibers are sintered, no bonding occurs even if re-melting is carried out. The reason for that is that the bonding is difficult because a melt viscosity of PTFE is as high as from 10.sup.10 to 10.sup.13 poises.
Therefore, when the above-mentioned PTFE fibers once sintered are bonded in the molten state, there is no way other than applying a big pressure, and as a result, shape as a fiber becomes irregular.
From the reason mentioned above, the method of producing a non-woven fabric from the PTFE fibers once sintered is limited. Namely, there have been no way other than simply intermingling the PTFE fibers by needle punching method or water jet needling method.
An object of the present invention is to provide the PTFE composite fiber having remarkably improved thermal bonding property, PTFE cotton-like materials which can be used to produce a non-woven fabric by thermal bonding, processes for production thereof, and processes for producing a split yarn, a monofilament and a multifilament having loop and/or branched structure.